Relationship between fractional exhaled nitric oxide and bronchopulmonary dysplasia in extremely/very low birth weight infants

Abstract

Objective To investigate the relationship between fractional exhaled nitric oxide (FeNO) and bronchopulmonary dysplasia (BPD) in extremely/very low birth weight infant (ELBWI/VLBWI). Methods Thirty-five ELBWI/VLBWI (gestational age <34 weeks at birth and birth weight <1 500 g), who were admitted to neonatal intensive care unit of Peking University Third Hospital from October 2014 to March 2015 with respiratory distress soon after birth, were enrolled into the study, and divided into BPD group (n=11) and non-BPD group 1 (n=24) according to the diagnosis at discharge. One day before they left the hospital, FeNO level was determined with Exhalyzer D, an equipment for pulmonary function test. Difference of FeNO and nitric oxide (NO) production between the two groups was compared with t-test or Fisher exact test, and the value of FeNO in predicting BPD was tested by receiver-operating characteristic (ROC) curve. Results The mean gestational age at birth in BPD group was significantly less than that in non-BPD group [(29.7±1.9) vs (32.0±1.5) weeks, t=4.005, P=0.000], and the duration of invasive ventilation [(53.0±91.3) vs (15.0±30.2) h, t=1.598, P=0.002] and oxygenation was longer [(42.1±7.8) vs (8.2±6.4) d, t=13.567, P=0.000]. There were more babies required surfactant treatment, prenatal cortisone administration, and inhalation of cortisone and bronchodilator during hospital stay in BPD group than in non-BPD group[10/11 vs 38%(9/24), 11/11 vs 58%(14/24) and 11/11 vs 21%(5/24), Fisher exact test, all P<0.05]. The age and body weight of the babies at the time of FeNO determination in BPD group were older or higher than those in non-BPD group [(46.4±16.3) vs (20.9±11.7) d, t=5.278, P=0.000; (2 090±164) vs (1 892±153) g, t=3.498, P=0.001], but the corrected gestational age was similar [(36.3±3.1) vs (35.0±2.3) weeks, t=1.407, P=0.169]. Both the mean FeNO level and NO production in BPD group were significantly higher than those in non-BPD group [(13.6±6.9) vs (8.0±3.6) ppb (1 ppb=1×10-9 mol/L), (25.6±10.1) vs (18.1±9.0) nl/min, t=2.967 and 2.478, P=0.006 and 0.018]. The area under the ROC curve was 0.749 (P=0.021, 95%CI: 0.539-0.953) which implied that FeNO provided medium power for discrimination of ELBWI/VLBWI with BPD from those without, with a sensitivity of 72.7% and specificity of 75.0% at the cut-off value of 11.55 ppb. Conclusions FeNO and NO production in BPD infants are significantly higher than non-BPD infants. Measurement of FeNO for ELBWI/VLBWI through mask before discharge is a simple, safe and invasive procedure to objectively evaluate pulmonary function early after birth. Key words: Bronchopulmonary dysplasia; Respiratory function tests; Nitric oxide; Infant, very low birth weight; Infant, extremely low birth weight